Photographic films having a stripping layer composed of a mixture of ethyl celluloseand cellulose nitrate



PHOTOGRAPHIC FILMS HAVING A STRIPPING LAYER COMPOSED OF A MIXTURE OF ETHYL CELLULOSE AND CELLULOSE NITRATE Filed NOV. 5, 1949 y 1953 c: F A. WHITE ET AL 1 2,638,417

DYED OR PIGMENTED GELATIN SILVER HALIDE EMULSI'ON INVENTORS CLAYTON F. A.WH/TE 8 JOHN C. H/LL Y @WEM ATTORNEY Patented May 12, 1953 PHOTOGRAPHIC FILMS HAVING A STRIP- PING LAYER COMPOSED OF A MIXTURE OF ETHYL CELLULOSE AND CELLULOSE NITRATE Clayton F. A. White, Stelton, and John R. Hill, Piscataway Township, Middlesex County, N. J assignors to E. I. du Pont de Nemours & Com- I pany, Wilmington, Del., a corporation of Delaware Application November 3, 1949, Serial No. 125,198

system has various disadvantages which are well known to those skilled in the art including long exposures to light because of their low sensitivity, no visible measure of the quality of the reproduction being provided until the gelatin relief image is formed, and a limited scale of tones.

An object of this invention is to provide an improved presensitized photographic stripping film for making gelatin relief images. A further object is to provide such a film which can be used in the photogravure process in place of the present carbon tissues. A still further object is to provide such a. film which will enable the technician to determine the quality of the reproduction before the gelatin relief image is formed. Still other objects will be apparent from the following description of the stripping film.

The presensitized stripping film of this invention consists of a hydrophobic cellulose carboxylic acid ester, e. g., cellulose acetate film base having one surface coated with a thin moisture-proofing "layer, e. g., composed of a vinyiidene chloride/- isobutylene or vinylidene chloride/acrylonitrile copolymer or cellulose nitrate which is coated with one or more layers of a water-permeable colloid, e. g., albumin, agar agar or gelatin. The opposite surface of the base is provided with a thin stripping membrane consisting of a water insoluble ethyl cellulose and cellulose nitrate on which there is coated a thin layer of a film-forming material which is soluble ina water-miscible organic solvent; Such film-forming materials include cellulose derivatives, e. g., cellulosenitrate, cellulose acetate, cellulose acetate-butyrate, cellulose acetate-propionate, cellulose propionate; polyvinyl esters, e. g., polyvinyl acetate, polyvinyl chloracetate and polyvinyl acetals, e. g., polyvinyl alcohol acetals of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and isobutyraldehyde. These water-insoluble, filmforming materials serve as aisuppo'rt for a thin gelatin sublayer which in' turn is coated with a l 8 Claims. (01. 95-9) gelatino silver halide emulsion layer. The emul sion contains a fugitive or a non-fugitive dye or pigment. A gelatin backing layer or a plurality ofsuch layers may be on the surface of the film opposite the emulsion layer. The backing layer or layers may be colorless or contain a pigment or dye which is preferably complementary in color to that of the silver halide emulsion layer.

It is emphasized that the light-sensitive gelatino silver halide emulsion layer should be soft, i. e., capable of being later differentially hardened in a developing or bleaching bath so that a relief image can be formed by washing away unhardened emulsion. In addition, the ratio of gelatin to silver halide is preferably high, i. e., a relatively large quantity of gelatin to a relatively small quantity of silver halide. A satisfactory range is from 2 to 5 parts of gelatin to 1 part of silver halide.

Various types of dyes and/or pigments can be used in the emulsion layer, but they should be of color which will contrast with the reflectance from the metal surface, e. g., plate or cylinder to which the gelatin emulsion layer is attached in making a gelatin resist. The surface is usually brightly polished copper and the dye or pigment may be yellow,orange, orange-red, brown, etc. The coloring matter serves as a visual aid to staging and etching operators when there is sufficient contrast to outline details of the relief images.

Ithas been found that the dyes or pigments used in the gelatino silver emulsion layer have the further advantage that they serve as lightabsorbers or filterslimiting the depth of exposure of the emulsion layer and causing the'image to be formed at the outer surface or in the outer stratum of the emulsion.

The gelatino silver halide emulsion layer in the elements may be sensitive to blue light only The stripping film of this example n will be described with reference to the accompanying drawing which constitutes part of this specification.

A. A cellulose acetate film base I having a thickness of about 0.005 inch is provided on one surface with a thin layer 2 of cellulose nitrate from a solution of about 4.4% solids in 10.6% methanol and 85% acetone by weight and the latter layer is;coated ,with a sublayer 3 of gelatin from an acid solution of about 1% gelatin, 57% methanol and 40% acetone and 2% water by weight.

B. A gelatin backing layer 4*.having .-azthickness of approximately 0.0010..inch.is.eoatedonto the sublayer from a solution containing the following ingredients, the amounts being in percent by weight:

4 mide emulsion of the type described in Example I there are added the following solutions:

Water 90.00 Gelatin 7.60

Glycerol 0.20 Chrome alum 0.00 Saponin l n .01.08 Carvacrol 0.03 Ethanol 2 :03

A stripping layer .5 consisting of two parts of ethyl cellulose and 1 part of cellulose nitrate is coated onto the other surface of the film base to a thickness of 0.0002 inch from a solution containing 5% of the mixture of ethyl cellulose and cellulose nitrate, 85% of acetone and monomethyl ether of ethylene glycol. A layer 6 approximately 0.0002 inch'in thickness composed of cellulose nitrate is coated onto layer 5from an acetone solution and a thin layer 1 of gelatin is coated onto. the cellulose nitrate layer. The ethyl cellulose of this example is of the water-insoluble type and is. a commercial product of medium viscosity and standard ethoxy content which is soluble in organic solvents, e. g., acetone, methanol, ethanol, methyl acetate, and toluene, but insoluble'in water. A preferred type has an ethoxy content of about'48%, but products of to are useful.

C. A gelatino silver halide positive type emulsion containinga non fugitive dye is prepared in the following manner and coated on sublayer l to a thickness of. 0.0015 inch to'form light-sensitive' layer" 8. This emulsion is prepared' inthe following mannerr'To 5kg. of a; finegrainposi- I tivextype 'gelatino silver iodobromide emulsion containing 1 mole percent AgI and 99' mole percent AgBr and a particle size of'0.1' to 1:0 micron which'has' been precipitated, ripened, washed and after-ripened in a conventional manner is admixed "the following solutions:

The speed of this emulsionais approximately that of a standardzfine grain-positive emulsion free: from the above fugitivev dye. and the extra gelatin.

A similar :fllm canine made by. eliminating. the cellulosenitrateeoatingl if desired.

Example II A stripping film is prepared after the manner Ofi Example I except. in place .of thesilver halide emulsionoi paragraph C there is used an emulsion containing a colloidal dispersionoi a ferric oxide pigment prepared in the following mannereand coated-on .layer 1 .to .amthickness of 0.0010. inch .to 5 l;g..ot lagelatino, silver. iodobropositive emulsion. free from the pigment and extra gelatin. The pigment dispersion referred to above is-obtained as a paste consisting of about 50% FezOaI-IzO and 50% free water. For instance, 240 grams of the paste and an equal part of water are placed in a glass or ceramic container along with any equal weight. of glass beads. After mild agitation 160. grams of a10% by weight citric .acid solution is introduced and the whole turned for 24 hours on a rolling mill. The pigmentis .at this point reduced to a yelloworange colloidal dispersion. The solution of gelatin is prepared as shown above and sodium hydroxide added in calculated quantity to fully neutralize the citric acid in the pigment dispersion. "The pigment dispersion is .next added to the alkaline gelatin solution with constant agitation and a colloidal dispersion of ferric oxide .in gelatin is obtained. The finished film when fixed free from silver halides has a nearly transparent orange-red color.

Example III A pping film support is-prepared exactly as in paragraph .A of Example I.

(B) A gelatin backing is prepared in the following. manner and coated on the side opposite the stripping membrane. it is coated to a thickness of 0.0010 inch. Ingredients of the'coa-tingpreparation are given in percentby Weight.

VSZater 89.75 Gelatin 7.60 Ink BlueR ((3-1. 707) 0.25 Glycerol 0.20 Chrome alum 0.06 Saponin 0.08 Carvacrol 0.03 Alcohol 2.03

(C) 'A' silver halide emulsion (8) containing the non-fugitive dye is preparedand coated upon the stripping membrane-exactly as .in Example. L

The backing layer 4 containing Ink Blue R has a deep blue color complementing the color of theemulsion. This arrangement comprises a distinct advantage. in rapid identification .01. the film "surfaces when. the product in .nse.

Example I V A stripping film support is prepared exactly as in paragraph A of Example I. A backing layer is added exactlyasin.paragraph B. of Example I.

(C) A'si1vernhalide emulsion (3) containing thernon-fugitive dye substanceof Example I and having a silver halide composition of '75 mole percent AgBr and 25 mole percent AgCl is coated toa thicknessof 0.0008 inch upon the stripping membrane.

The emulsion, gelatin-dye solution, and other additions are the same as in Example I except that no KBr is added before coating. The photographiccharacteristics of this. film differ fromi the preceding examples in thatthe contrastis higher and the speed approximates that of a typical microfilm. The grain size-is smaller than in cine positive and is inthe order of.-i.0.5e0.5 micron.

The invention is not limited to the specific proportions of ethyl cellulose and cellulose nitrate which ar given in the foregoing examples, although the 2 to 1 ratio is preferred for a thickness of approximately 0.001 inch for the-emulsion layer. To the contrary, a range of 6 to 9 parts of ethyl cellulose to 4 to 1 part of cellulose nitrate is suitable. Within this range increasing the ethyl cellulose content results in decreasing 'adhesion to the main support which admits of greater ease in stripping. These proportions are critical, however, because if more than 9 parts of water-insoluble ethyl cellulose per part of cellulose nitrate is used the layers tend to strip spontaneously during drying. If less than 1 /2 parts of the former per part of cellulose nitrate is used the degree of adherence is too great and separation'cannot be accomplished.

The thickness of the various layers may vary somewhat from those given in the examples. In the case of stripping layer 5 a practical range is from 0.00008 to 0.0003 inch. The minimum thickness is that required to maintain a coherent film without tearing or distortion when the emul sion coating is firmly attached to a rigid surface, e. g., a metal printing plate or cylinder and the temporary support stripped away.

Various coloring substances, e. g., dyes or pigments can be used in the emulsions. The colors,

however, should as stated above contrast withv the reflectance from the metal surface to which the resist is attached which is usually brightly polished copper. Suitable additional dyes which can be used in non-color sensitized emulsions are Pontamine Fast Orange (C. I. #326), Pontamine Fast 'Red 8 Bl (C. I. #278). Mixtures of these dyes also can be used. In general, it is advisable to use dyes which are not complementary in color to the reflectance from the metal surfaces because the resulting neutral shade would interfere with observation of etching. The etched tones first appear as grey to black when observed through the resist.

Various photographic senitizing dyes can. be added to the emulsions if desired to extend their sensitivity to the green and red regions of the spectrum if desired. There are a large number of such dyes known and available and they include the simple cyanine, carbocyanine, pseudocyanine, kryptocyanine, merocyanine and styryl dyes, etc.

The stripping film elements of this invention are as stated above useful for the making of reliefs in photogravure and like processes of reproduction.

An advantage of the films is that they are commercially practical and can be made with the conventional coating equipment of photographic manufacturers. Another advantage is that the stripping layer has fair adhesion when dry or wet, but can be readily stripped when dry by the application of mechanical force. A further advantage is that the film provides a means for determining the quality of a photographic reproduction before the etching stage in a photogravure process. Still further advantages are that the films are dimensionally stable and can reproduce a wide range of tones. Still other advantages 6 will be apparent from the above description of the invention.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except as defined by the claims.

What is claimed is: e

1. A photographic stripping film comprising a hydrophobic cellulose carboxylic acid ester film base having one surface coated in order with a thin moisture-proofing layer and a water-permeable colloid backing layer and the other surface of said base coated in order with a stripping membrane composed of a mixture of water-insoluble ethyl cellulose and cellulose nitrate in the proportion of 6 to 9 parts of the former to 4 to 1 part of the latter, a thin layer composed of a water-insoluble, film-forming material selected from the group consisting of cellulose esters, polyvinyl esters and polyvinyl acetals, and a gelatino silver halide emulsion layer containing a coloring substance.

2. A photographic stripping film comprising a hydrophobic cellulose carboxylic acid ester film base, having one surface coated in order with a thin layer of nitrocellulose, a thin anchoring substratum of gelatin and a gelatin backing layer and having the other surface of said base coated in order with a stripping membrane composed of a mixture of a water-insoluble ethyl cellulose and cellulose nitrate containing about 6 to 9 parts of the former to 4 to 1 part of the latter, a thin layer composed of a hydrophobic cellulose ester, a thin gelatin substratum and a gelatino silver halide emulsion layer containing a coloring substance. v

3. A photographic stripping film comprising a hydrophobic cellulose carboxylic acid ester film base, having one surface coated in order with a thin layer of nitrocellulose, a thin anchoring substratum of gelatin and a gelatin backing layer and having the other surface of said base coated in order with a stripping membrane composed of a mixture of a water-insoluble ethyl cellulose and cellulose nitrate containing about 6 to 9 parts of the former to 4 to 1 part of the latter, a layer having a thickness from 0.00008 to 0.0003 inch composed of a water-insoluble cellulose ester, a thin gelatin substratum and a gelatino silver halide emulsion layer containing a coloring substance.

4. A photographic stripping film comprising a hydrophobic cellulose acetate film base bearing on one side in order a, thin cellulose nitrate layer, a gelatin anchoring substratum and a backing layer composed of gelatin and has on the other surface, in order, a stripping membrane composed of water-insoluble ethyl cellulose and cellulose nitrate in the proportions of 6 to 9 parts of the former to 4 to 1 part of the latter, a thin membrane composed of cellulose nitrate, a thin gelatin anchoring substratum and a gelatino silver halide emulsion layer containing a dye.

5. An element as set forth in claim 3 wherein the gelatino silver halide emulsion layer contains a non-fugitive dye which is yellow to red in 7 8 8. A.photographic,stripping-2111mm"awh'imib i Name Date in claim 3 wherein the gelatino silveraihailide 22,146,)?! miiardeau .et a l. ,Feb; 1%, 1939 emulsion sontains a yellow-.orange;colloidal+dis- 2,3533; :wmt N 23, 1944 persionof FeaOaHzO. 52392503 Rutter Jan. 8, 1946 CLAYTON F. .A. WHITE. 5 2,409,564 :Heinecke .Oct. 15, 1946 JOHN B. .HILL. 2,491,023 Alles et a1 Dec. 13, 1949 References Cited in the file of-this patent B I AT UNITED STATES PATENTS Qountry Date Number Name 10 .aasmau ,lGre-a tpBritam V Dec. '7, 1929 1,432,366 .sulzer 00117, 1922 GreatBritam F Feb. 26, 1934 

1. A PHOTOGRAPHIC STRIPPING FILM COMPRISING A HYDROPHOBIC CELLULOSE CARBOXYLIC ACID ESTER FILM BASE HAVING ONE SURFACE COATED IN ORDER WITH A THIN MOISTURE-PROOFING LAYER AND A WATER-PERMEABLE COLLOID BACKING LAYER AND THE OTHER SURFACE OF SAID BASE COATED IN ORDER WITH A STRIPPING MEMBRANE COMPOSED OF A MIXTURE OF WATER-INSOLUBLE ETHYL CELLULOSE AND CELLULOSE NITRATE IN THE PROPORTION OF 6 TO 9 PARTS OF THE FORMER TO 4 TO 1 PART OF THE LATTER, A THIN LAYER COMPOSED OF A WATER-INSOLUBLE, FILM-FORMING MATERIAL SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ESTERS, POLYVINYL ESTERS AND POLYVINYL ACETALS, AND A GELATINO SILVER HALIDE EMULSION LAYER CONTAINING A COLORING SUBSTANCE. 